1. Field of the Invention
The present invention relates to a semiconductor device package of a plurality of stacked semiconductor chips.
2. Description of Related Art
With a decrease in the size of mobile phones and portable equipment, demand for reducing the size of semiconductor devices used therefor is increasing. As an approach to meeting this demand, a technique to stack a plurality of semiconductor chips in one package is proposed. This technique is described in Japanese Unexamined Patent Application Publications No. 2002-261233 and 2002-57272, for example. FIG. 5 shows a configuration example of a semiconductor device using this technique.
As shown in FIG. 5, a semiconductor chip 3a is bonded to a substrate (interposer) 2 with adhesive, and a semiconductor chip 3b is placed thereabove with a spacer 4 interposed therebetween. The spacer 4 is placed in order to create a space for connecting a wire to an electrode of the lower semiconductor chip 3a. The spacer 4 and the semiconductor chips 3a and 3b are bonded with adhesive, for example. The electrode of the semiconductor chip 3a is connected to an electrode of the substrate 2 by a wire 5a. An electrode of the semiconductor chip 3b is connected to an electrode of the substrate 2 by a wire 5b. The semiconductor chips 3a and 3b, the spacer 4, and so on are packaged by a sealing resin 6.
In a conventional semiconductor device shown in FIG. 5, the spacer 4 needs to be located inward at a certain distance from a peripheral area of the lower semiconductor chip 3a where electrodes are placed since it is necessary to create a space for connecting a wire to those electrodes. Thus, if the upper semiconductor chip 3b placed on the spacer 4 is significantly larger than the spacer 4, flexure of the semiconductor chip 3b can occur since the spacer 4 supports the semiconductor chip 3b only at a small portion at the center of the chip. This can lead to bad bonding or deterioration in the quality of the semiconductor chip 3b. 
Further, the sealing resin 6 is normally injected in one direction as shown in FIG. 6, which is in the direction of an arrow, for example. Thus, the density of the sealing resin 6 is low in an area 7 located in the vicinity of the spacer 4 and in the opposite side of the injection side, which causes a void to occur in this area. The spacer 4 is relatively thick due to its purpose of creating a certain space for connecting a wire to the electrode of the lower semiconductor chip 3a. Accordingly, the void occurring in the area 7 is large. The large void causes the package of the semiconductor device to be fragile and breakable.